<!DOCTYPE html>
<html>
<head>
  <style>

  .red { color:red; }
  </style>
  <script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body>
  <span>Hello</span>
  <div></div>
  <div></div>
  <div></div>
<script>$("div").html("<span class='red'>Hello <b>Again</b></span>");</script>

</body>
</html>